\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,scale=1.0]
	\draw (0,0)--(6,0)node [right]{$B$};
	\draw (0,3)--(6,3)node [right]{$A$};        
	\foreach \x in {.5,1.5,...,5.5}
	{
		\node at (\x, 0.25){$+$};
		\node at (\x, 2.75){$-$};
	}
	\fill (2,2.7) circle (2pt);
	\fill (5,.3) circle (2pt);
	\node at (2,2+.4){$P_1$};
	\node at (5,1-.4){$P_2$};
\end{tikzpicture}
\end{document}